Cookware, of course, is used to hold and apply heat to food during preparation of the food. Exemplary pieces of cookware include stock pots, woks, frying pans and the like. As used herein, the word “cookware” refers generically to any of these and similar types of cookware. Although cookware comes in many different shapes and sizes, all cookware includes two basic elements: a first surface for receiving thermal energy from a heat source, i.e., the “heat-receiving surface,” and a second surface for applying the heat to raw food to be cooked, i.e., the “cooking surface.” In the case of conventional cookware, the heat-receiving surface and the cooking surface are the two opposing faces of a monolithic or laminar sheet of heat-transfer material—typically steel, copper, copper-coated steel, aluminum, these materials with the cooking surface further coated with an non-stick material, and the like.
Cooking itself is a straightforward process and well known. In a typical process for cooking food, a piece of cookware holding the raw food to be cooked (or the raw food plus a liquid medium, such as water or cooking oil) is placed on a gas range having a burner. When ignited, the burner produces a flame that rises up in response to the pressure of the gas in the range's supply piping. The buoyancy of the hot air causes the flame to touch the heat-receiving surface of the cookware—i.e., the bottom of the pan. Thermal energy is transferred from the flame to the heat-receiving surface of the cookware via convection as well as thermal radiation. Thus, the heat-receiving surface absorbs the thermal energy from the burning gas from the range. Thermal conduction then transfers the thermal energy from the heat-receiving surface to the cooking surface of the cookware. The rate and efficiency of the heat transfer is a function of the material from which the cookware is made (for example, steel vs. copper vs. aluminum). The cooking surface of the cookware then transfers thermal energy to the food to be cooked via conduction and convection.
The efficiency and rate at which the heat is transferred from the heat-receiving surface to the cooking surface for any given piece of cookware is dictated in major part by the heat capacity and the specific heat of the material from which the cookware is made. These two measures are sometimes confused: Heat capacity is the ratio of the amount of energy absorbed by the material to the associated temperature rise of the material (that is, energy input/temperature rise, for example Joules/Kelvin). Thus, materials having a low heat capacity are desired for cookware because a small amount of input energy yields a larger associated temperature rise. Specific heat is the heat capacity of a material per unit of mass (energy input/(temperature)(mass), for example, Joules/(gram)(Kelvin)). Again, materials having relatively low specific heats are desirable for cookware because they transfer heat efficiently. Because metals have very low heat capacity and specific heat, they are conventionally used for cookware. For example, iron has a specific heat of 0.444 J/g° C. The specific heat of aluminum is 0.900 J/g° C.; the specific heat of copper is 0.385 J/g° C. The low specific heat of copper thus makes it desirable as a cookware material.
A drawback, of course, is that metals are heavy. Thus, while cast iron skillets and Dutch ovens are well known for their desirable cooking characteristics, cast iron cookware is very, very heavy. Aluminum gives the benefit of lighter weight, but lower thermal efficiency. Whatever metal is chosen, cookware tends to be bulky and difficult to store. Thus, there remains a long-felt and unmet need for cookware that is both thermally efficient and easy to store.
Throughout all of the figures, the same reference numerals are used to identify the same structures.